Method for the preparation of cement



1967 TADASHI ASANO METHOD FOR THE PREPARATION OF CEMENT Filed De. s. 1963 -o 16 20 304050, 60 10 80 90100 CALCIUM 0x105 (w \09 0 80 70 so 5040 so 20 lo 0 CALCIUM CARBONAT E (/e) \o 20 so 40 so so 10 so 90100 CALCIUM oxloE w.)

I00 90 8O 7O 6O 5O 40 3O 20 l0 0 CALCIUM CARBONATE (/o) Unitcd States Patent Ofi 3,298,843 Patented Jan. 17, 1 967 ice Japan Filed Dec. 3, 1963, Ser. No. 327,608 Claims priority, application Japan, Dec. 13, 1962, 37/551160 4 Claims. (Cl. 106100) This invention relates to a method for the preparation of cement by molding a cement raw mixture comrial in the ratio of the calcium'oxide to the calcium carbonate being above 45.4:54.6 into molded articles and calcining said molded articles. In accordance with one modification of this invention a cement raw mixture contains at least one binder as an additional component selected from the group consisting of water, alkaline earth metal hydroxides, mineral oils such as heavy oil, vegetable oils such as soybean oil, spent liquors from pulp making, natural and synthetic plastic materials.

Raw materials used in this invention were analyzed and the results were shown in the following Table l together with their particle sizes.

TABLE 1 88 Sieve Chemical Components (Percent) Items Residue Y i r (Percent) Igfiition SiO; A1103 FezOa CaO MgO Total oss Raw Materials: I i v I Lime Stone 2. 42. 6 2. 5 r 0. 4 0. 1 53. 7 0. 6 99. 9 2. 0 4. 1 4. 2 0. 7! .0. 2 89. 5 1. O 99. 7 0. 9 i 8. 8 59. 3 19. 0 8. 1 0. 8 3. 0 99. 0 0.9 2.2 89.8 5.0 1.7 0.5 0.8 100.0 0. 9 34. 7 8. 4 43. 8 11. 2 i 2. 4 100. 5

prising calcium oxide and-calcium carbonate as a calcium raw material in a specifiedratio under pressure into molded articles and calcining said molded articles.

There has already been practised a method for the preparation of cement by calcining a cement raw mixture in powder state comprising lime stone or quick lime as a calcium raw material. And also it has been Well known that the calcination of a cement raw mixture comprising substantially quick lime as a calcium raw material is more easily carried out as compared with that of a cement raw mixture comprising calcium carbonate as a calcium raw material.

However, when such a cement raw mixture is used for the preparation of cement, a considerable large amount of the raw mixture escapes into the flue from a cement kiln and is lost as dust. This causes difficulty in the preparation of cement having a desired composition and therefore the dust has been usually recovered by using a device such as an electric collector having a large capacity. I

Also, there has been planned a method for the preparation of cement by compressing molding a cement raw mixture comprising calcium carbonate as a calcium raw material into molded articles and calcining said molded articles but the method has not been practised since such a raw cement mixture cannot be compressed easily and does not result in a high yield of molded articles.

Now the inventor has developed this invention in order to overcome the defects adherent to the prior art.

An object of this invention is to provide a method for the preparation of the molded articles with a high yield by molding a cement raw mixture comprising calcium oxide and calcium carbonate as a calcium raw material in the specified ratio as defined hereinafter.

Another object of this invention is to provide an economical method for the preparation of a high grade cement by calcining the molded articles in a kiln with a high thermal efficiency and reducing the amount of dust.

Other objects of this invention will be obvious from the detailed description hereinafter.

In accordance With this invention a method is comprised the steps of molding a cement raw mixture comprising quick lime and lime stone as a calcium raw mate- The quick lime in the table was prepared by calcining lime-stone and it contained calcium carbonate in' an amount of about 4.6% by Weight of calcium oxide.

And the copper slag was a by-product from a copper refinery.

The cement raw mixtures of Nos. 1 to 11 as shown in Table 2 and having the chemical composition to meet the following Equations 1 to 3 were prepared by using the raw materials as shown in Table 1.

It should be noted that thecement raw mixture contains the calcium oxide and calcium carbonate in varied amounts as shown in the following Table 2.

TABLE 2 Mixing Ratios (Percent) Items CaCOs CaO. Alumina; Silica Copper Slag Nos. of Cement Raw Mixture:

For a better understanding of the nature and objects as described above of this invention, reference should be had to the detailed explanation and an example hereinafter given in combination with the accompanying drawings in which:

FIGURE 1 is a curve showing the relationship between a free calcium oxide contained in a clinker and the ratio Further, in another modified embodiment of this invention, the cement raw mixture can be prepared under a reduced atmospheric pressure and the molding can easily be carried out as compared with the normal convenof lime-stone to quick lime in the raw mixture. 5 tional operation due to the absence of air contained therein.

FIGURE 2 is a curve showing the relationship between As illustrated above, this invention has the advantages molded articles retained on a 5 mm. sieve and a mixing that a high grade cement can be produced with the ratio of lime-stone to quick lime. smoothness of calcination, a high thermal efficiency and The clinker illustrated in FIG, 1 was made as follows: the du tio of an mount of du t,

A raw mixture of cement was compressed between rollto This invention is illustrated by the following example. CYS under pressure of 100 kg/om? into a form of sheet The lime as shown in Table 1 was crushed to the powahd the Sheet Was into Chips having a Size as desireddered particles having a 20% retained on the 88 sieve. Raw mixtures of cement including calcium oxide and Al i ili d copper l were i d t th i calcium carbonate in proportions varying, as illustrated h ratio f l i ili d o r la being in FIG. 1, from 0% calcium oxide and 100% calcium car- 6071274119 bonate to 100% calcium oxide and 0% calcium carbonate were employed Five grams of the chip were charged respectively and then the H11XtLlI'C WaS crushed to powinto a platinum crucible. An electric furnace was heated dgred pamcles hFwmg a 09% retamed P 8 slave at 1000 C. and then the platinum crucible was located A cement raw mlxture was prepared-by mlxmg the 3 in the electric furnace and the temperature of the elec- P oxldc and the latter powderedmlxture tric fumzlet3 was raised to a temperature of 14500 for in a ratio by weight of the former to the latter being 70.5 over one hour and maintained at that temperature for 15 to minutes to produce clinker. The clinker was then cooled Three kmds of chrfker were prepared by the and analyzed in order to measure the content of free Sulted cement raw mlxture as follows: calcium oxide therein In the first case the cement raw mixture was com- As Seen from FIGURE 1! the inventor f d that the pressed between rollers under pressure of 100 kg./cm. content of the free calcium oxide of the clinker is sharply into a Sheet having a thickness of about 15 m f the decreased When the ratio of the calcium Oxide to the sheet was charged into a pilot rotary kiln having a size of calcium carbonate i above 45.4;54,6 800 mm. diameter and 8000 mm. length at a rate of Also, as seen from FIGURE 2, the inventor found that 30 240 kg/hfcalcined a temperature of 1450 the sheet can not be formed with a high yield, as shown to p a clinkar-v by the percent residue retained on the 5 mm. sieve, when In the Second Case, the Same Cement raw mixture was the cement raw mixture is prepared by excluding the miXed With a hgnin Spent liquor P- in an calcium oxide as the calcium raw material, but that the amount of 6% y Weight of Said raw mixture and then yield increases when the calcium oxide is used together the mixture was subjected to the compression and the with the calcium carbonate as the calcium raw material calcination in the same manner as in the first case. in the cement raw mixture, and particularly the yield is In the third case, the same cement raw mixture was disharply increased when the cement raw mixture contains rectly charged into the same pilot rotary kiln as in the the quick lime and lime-stone as the calcium raw matefirst case at a rate 182 kg./hr. and calcined in the same rials in a ratio of calcium oxide to calcium carbonate of 40 manner as in the first case. above 35 .4:64.6. The results are shown in the following table.

TABLE 3 Rate of Caleination Total Thermal Free CaO Dust Kinds of Charge Binder I Charge Output Temperature Consumption Contained in Recovered (kg/hr.) (kg/hr.) C.) in (10 kcaL/ Clinker (kg/clinker clinker ton) (percent) ton) Compressed 240 212 1, 450 2, 940 0.23 47 0 Liguiu Spent Liquor 240 212 l, 450 3,020 0. 24 42 Powdered 182 152 1, 450 3, 610 o. 25 105 In accordance with this invention it should be under- What I claim is: stood that the lime as shown in Table l is substituted by 1. A method for the preparation of cement which coinany lime regardless of its content of calcium carbonate prises preparing a powdered raw cement mixture includand therefore any calcium oxide can be used together with ing as calcium raw materials calcium oxide and calcium calcium carbonate so far as the ratio of the calcium oxide carbonate, the ratio by weight of said calcium oxide to to the calcium carbonate is above 45 .4:54.6 as mentioned aid 1 i a b t being above 45.4;545, compressabove. ing said raw cement mixture as a powder into molded The cement raw mixtures are compressed under presti l d l i i id Compressed i l Sure Q f 50 kg/ CD152 Q ohthln molded articles Which 2. A method for the preparation of cement according do not disintegrate during handling. to claim 1 wherein said powdered raw cement mixture is However, in one modified embodiment of this invencompressed at a pressure b 50 k r1011, the compresslon can b lowered) below 0 ka c5 3. A method for the preparation of cement which when the binders as described herembefore are added to comprises preparing a powderedtaw cement mixture the cement raw mtxtufe as y g an excelhiht eluding as calcium raw materials calcium oxide :and calto the molded artlcles- Fddltlofl, y p Cfirtam cium carbonate, the ratio by weight of said calcium oxide advantages that the calcination of the molded articles can t id l i carbonate b i ab ve 45 4;54 and be earned t Wlth smoothhes as mp h a cluding at least one binder, compressing said raw cement Cement h II11Xtuf6 not contalhlng sald blhdfif, t With mixture as a powder into molded articles, and calcinin a reduction in the amount of the kiln dust. The binders id compressed articles. should be used in an amount of below 6% by weight of 4. The method according to claim 3, wherein at least the cement raw mixture because their excessive amount one binder selected from the group'consisting of water, tends to disintegrate the molded articles.

alkaline earth metal hydroxides, mineral oils, vegetable 031s, spent liquors from pug m aking, natural and syn- OTHER RE FERENCES 6oitlif$n$$$iai$513335553? 35 5211112155110222122121102?:52?

References Cited by the Examiner 5 P 128,

UNITED STATES PATENTS HELEN M. MCCARTHY, Acting Primary Examiner. 2,860,061 11/1958 Heilmann 106-400 TOBIAS LEVOW,

FOREIGN PATENTS 10 S. E. MOTT, Assistant Examiner.

1,884 1/1884 Great Britain. 

1. A METHOD FOR THE PREPARATION OF CEMENT WHICH COMPRISES PREPARING A POWDERED RAW CEMENT MIXTURE INCLUDING AS CALCIUM RAW MATERIALS CALCIUM OXIDE AND CALCIUM CARBONATE, THE RATIO BY WEIGHT OF SAID CALCIUM OXIDE TO SAID CALCIUM CARBONATE BEING ABOVE 45.4:54.6, COMPRESSING SAID RAW CEMENT MIXTURE AS A POWDER INTO MOLDED ARTICLES AND CALCINING SAID COMPRESSED ARTICLE. 